Module 3 Section 2 : Heart Activity

Question 1

What type of muscle controls regular beating of the heart

Answer 1

Cardiac muscle

Question 2

Cardiac muscle is…..

Answer 2

Myogenic

Question 3

Why is the heart said to be myogenic

Answer 3

It can contract and relax without receiving signals from nerves. This patterns of contractions controls the regular heartbeat

Question 4

Where does the process of producing a heartbeat start

Answer 4

At the sino-atrial node (SAN)

Question 5

Where is the SAN located

Answer 5

In the wall of the right atrium

Question 6

What is the SAN also known as

Answer 6

The pacemaker

Question 7

How does the SAN set the rhythm of the heartbeat

Answer 7

It sets the rhythm of the heartbeat by sending out regular waves of electrical excitation to the atrial walls

Question 8

The wave of electrical excitation causes what

Answer 8

It causes the right and left atria to contract at the same time

Question 9

What prevents the wave of electrical excitation from being passed directly from the atria to the ventricles

Answer 9

A band of non conducting collagen tissue prevents the wave of electrical excitation from being passed directly from the atria to the ventricles

Question 10

Because of the non conducting layer how does the wave of electrical excitation start its journey towards the walls of the ventricles

Answer 10

The wave of electrical excitation travels from the SAN across the atria to the AVN

Question 11

What does the AVN stand for

Answer 11

Atrioventricular Node

Question 12

What is the AVN responsible for

Answer 12

Passing the waves of electrical excitation on to the bundle of his. But there is a slight delay

Question 13

Why is there a slight delay before the AVN reacts

Answer 13

It delays to make sure the ventricles contract after the atria have emptied

Question 14

What is the bundle of his

Answer 14

The bundle of his is a group of muscle fibres responsible for conducting the waves of electrical excitation to finer muscle fibres in the right and left ventricles walls

Question 15

What are purkinje fibres

Answer 15

Finer muscle groups in the right and left ventricle walls

Question 16

The purkinje fibres carries the….

Answer 16

Wave of electrical excitation into the muscular walls of the right and left ventricles causing them to contract simultaneously, from the bottom up

Question 17

Describe the pathway of the wave of electrical excitation

Answer 17

• SAN emits wave of electrical excitation
• Wave of electrical excitation spread across atria
• Non conducting layer stops wave from passing from atria to ventricles
• Delay before AVN reacts so ventricles contract after atria empties
• Wave is picked up by the AVN
• The Wave travels down the bundle of his
• the wave branches out into purkinje fibres
• purkinje fibres carries the wave to the left and right ventricle walls causing them to contract simultaneously

Question 18

How does a doctor check someone’s heart function

Answer 18

By using an electrocardiograph

Question 19

What is an electrocardiograph

Answer 19

A machine that records electrical activity of the heart

Question 20

What does an electrocardiograph record

Answer 20

It records when the heart muscle depolarises when it contracts and repolarises when it relaxes. It does this by placing electrodes placed on the patients chest

Question 21

What is the P wave

Answer 21

• The P wave is the contraction (depolarisation) of the atria. AKA - Atrial systole.
• Identifiable by the first bump of the full heartbeat trace

Question 22

What is the QRS complex

Answer 22

• The main peak of the heartbeat, together with dips at either side
• First dip = Q
• The peak = R
• Second dip = S
• Caused by contraction (depolarisation) of the ventricles. AKA - ventricular systole

Question 23

What is the T wave

Answer 23

The T wave is due to relaxation (repolarisation) of the ventricles (Diastole)

Question 24

What does the height of the wave indicate

Answer 24

How much electrical charge is passing through the heart. A bigger wave means more electrical charge so for the P and R waves a bigger wave means a stronger contraction

Question 25

How do doctors use ECG’s to diagnose heart problems

Answer 25

Doctors compare their patients ECG’s with a normal trace. This helps them to diagnose any heart problems

Question 26

What is tachycardia

Answer 26

• A heartbeat that is too fast. Around 120bpm.
• may be ok during exercise but at rest it shows the heart isn’t pumping blood efficiently

Question 27

What is Bradycarida

Answer 27

• A heartbeat that is too slow - below 60bpm
• people may have because they are fit - training makes the heart beat slower and efficient
• severe bradycardia can be severe and may require an artificial pakemaker

Question 28

What is an ectopic heartbeat

Answer 28

• An extra heartbeat
• Caused by an earlier contraction of the atria than in the previous heartbeats.
• signalled by the P wave looking different and that it comes earlier than it should)
• it can be caused by early contraction of the ventricles too
• Occasional ectopic heartbeats in a healthy person don’t cause a problem

Question 29

What is fibrillation

Answer 29

• A really irregular heartbeat
• The atria or ventricles completely lose their rhythm and stop contracting properly
• Can result in anything from chest pains and fainting to lack of pulse and death